Used in Diablo II refering to when you get killed without collecting your corpse first, and when you having got your items/clothing on. Often happens when people cannot kill you when you have items on or want to steal all your gold.

Diablo 2 LOD term, short for naked kill. In dueling on Diablo 2 LOD, when you die, you come back to life in town and without gear. You must run out of town to retrieve your body, which is when NK occurs.

1. Not kidding! - Means the speaker is not kidding. It is the antonym of the acronym: Jk, which means just kidding. Therefore, Nk means that the speaker was not kidding instead of really kidding. Usually used as an insult or otherwise.

2. No kidding? - Means the respondent is asking if the speaker is not joking.

3. No Kissing. - Means the kind of thing you do not want your significant other, girlfriend or boyfriend to say during intimacy or otherwise

1.

Timothy: Your girlfriend is a freak...
Francis: Are you kidding?
Timothy: Nk.